A popular lament is that "they just don't build 'em like they used to" -- from toasters to telephones to tractors. We take no position on those products. But in the case of interplanetary spacecraft, the old saying may have some merit.
In particular, two craft launched in the 1970s to study the outer planets of our solar system are still going. In fact, they've reached the inner boundary between the solar system and interstellar space. In a few years, they should leave the solar system entirely. And with a little luck, they'll keep on working for years longer.
The craft are Voyagers 1 and 2. Both of them completed their main missions by the end of the 1980s. But their instruments were still working, and they still have plenty of power, so they've continued to study interplanetary space.
They've especially studied the solar wind, a flow of electrically charged particles from the Sun. These particles fill a magnetic "bubble" that surrounds the solar system.
In December of 2004, Voyager 1 crossed the inner edge of this bubble. It's where the galaxy's magnetic field begins to overpower the Sun's magnetic field. Voyager 2, heading in a different direction, crossed the boundary in 2007.
Right now, both craft are zipping through the turbulent zone that separates the Sun's magnetic bubble from interstellar space. They should exit that zone in a few years -- and provide the first direct observations of the conditions between the stars.
Script by Damond Benningfield, Copyright 2008
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